CHEMICAL SCIENCE. 287 



of the most prominent of agricultural facts could be satisfactorily explained. 

 Comparing the amount of nitrogen yielded in the different crops, when 

 grown without nitrogenous matter, as above referred to, with the amount 

 falling in the measured aqueous deposits, as ammonia and nitric acid, it 

 appeared, taking the average result of the analyses of three years' rain, that 

 all the crops yielded considerably more, and some very much more, than so 

 came down to the soil. The same was the case when several of the crops 

 had been grown in an ordinary rotation with one another, but without ma- 

 nure, through two or three successive courses. "Was this observed excess in 

 the yield over the yet measured sources at all materially due merely to 

 exhaustion of previously accumulated nitrogenous compound within the 

 soil ? Was it probably attributable chiefly to the absorption of ammonia or 

 nitric acid, from the air, by the plant itself, or by the soil ? Was there any 

 notable formation of ammonia or nitric acid from the free nitrogen of the 

 atmosphere? Or did plants generally, or some in particular, assimilate this 

 free nitrogen ? As already intimated, some of the points which had been 

 alluded to were at the present time under investigation. Others, it might be 

 hoped, would receive elucidation in the course of time. There, of course, 

 still remained the wider questions of the original source, and of the distribu- 

 tion and circulation of combined nitrogen in the soil, in animal and vegeta- 

 ble life on the earth's surface, and in the atmosphere above it. 



BOUSSINGAULT'S RESEARCHES UPON THE RELATION OF NITROGEN 

 AND THE NITRATES TO THE SOIL AND VEGETATION. 



Several years ago Boussingault demonstrated, in the clearest way, that 

 plants are incapable of assimilating the free nitrogen of the atmosphere. 

 Two years ago, in a paper communicated to the French Academy of Sci- 

 ences, he showed that nitrates eminently favor vegetation. He now shows, 

 by decisive experiments 



(1). That the amount, even of ternary vegetable matter, produced by a 

 plant, depends absolutely upon the supply of assimilable nitrogen (ammonia 

 and nitrates). A plant, such as a sunflower, with a rather large seed, may 

 grow in a soil of recently calcined brick, watered with pure water, so far as 

 even to complete itself by a blossom ; but it will only have trebled or quad- 

 rupled the amount of vegetable matter it had to begin with in the seed. In 

 the experiments, the seeds weighing 0'107 grammes, in three months of veg- 

 etation formed plants, which, when dried, weighed only 0'392 grammes, a 

 little more than trebling their weight. The carbon they had acquired from 

 the decomposition of carbonic acid of the air was only 0'114 grammes; the 

 nitrogen they had assimilated from the air in three months was only 0'0025 

 grammes. 



(2.) Phosphate of lime, alkaline salts, and earthy matters, indispensable to 

 the constitution of plants, exert no appreciable action upon vegetation, 

 except when accompanied by matters capable of furnishing assimilable ni- 

 trogen. Two plants of the same kind, grown under the same conditions as 

 above, but with the perfectly sterile soil adequately supplied with phosphate 

 of lime, alkali, in the form of bicarbonate of potash, and silex, from the 

 ashes of grasses, resulted in only 0'498 grammes of dried vegetable matter, 

 from seeds weighing 0-107 grammes ; and had acquired only 0'0027 grammes 

 of nitrogen beyond what was in the seeds, 



(3.) But nitrate of potash, furnishing assimilable nitrogen, associated 



